Anesthesiology
-
Local anesthetics interact with human ether-a-go-go-related gene (HERG) channels via the aromatic amino acids Y652 and F656 in the S6 region. This study aimed to establish whether the residues T623, S624, and V625 residing deeper within the pore are also involved in HERG channel block by bupivacaine. In addition, the study aimed to further define the role of the aromatic residues Y652 and F656 in bupivacaine inhibition by mutating these residues to threonine. ⋯ The authors' results indicate that not only the aromatic residues Y652 and F656 but also residues residing deeper within the pore and close to the selectivity filter of HERG channels are involved in inhibition of HERG channels by the low-affinity blocker bupivacaine.
-
Recently, it has been appreciated that in addition to their antinociceptive properties, opioid analgesics also can enhance pain sensitivity (opioid-induced hyperalgesia [OIH]). OIH may enhance preexisting pain and contribute to dose escalation, tolerance, and misuse/abuse of opioids. Better information is needed to determine which opioid or opioid combinations may be least likely to produce OIH and therefore possibly represent better choices for pain management. Herein the authors have examined the hyperalgesic and antinociceptive properties of racemic methadone and its enantiomers alone and in combination with morphine in rats. Methadone is of particular interest because it possesses both micro-receptor agonist and N-methyl-d-aspartate receptor antagonist activities. ⋯ The current findings with methadone are supportive of previous findings implicating mu-opioid and N-methyl-d-aspartate receptor mechanisms in OIH. Better understanding of OIH may help in choosing the most appropriate opioids for use in the treatment of pain.
-
The effects of high-dose morphine on vascular endothelial function have not been previously shown. The authors hypothesized that the pro-oxidant effect of high-dose morphine impairs vascular endothelial function. ⋯ Collectively, the authors' results showed that high-dose morphine impairs vascular endothelial function via attenuation of biologic activity of endothelium-derived nitric oxide. Chemical antagonism between superoxide anions generated by nicotinamide adenine dinucleotide phosphate oxidases may be the molecular mechanism responsible for the inactivation of endogenous nitric oxide after treatment with high-dose morphine.
-
A single dose of the macrolide antibiotic erythromycin can induce tolerance against cerebral ischemia in vivo (pharmacologic preconditioning). This study identified potential mechanisms of tolerance induction by assessing effects of erythromycin preconditioning on the cerebral transcriptional response to transient global cerebral ischemia. ⋯ These findings present a new molecular correlate for the induction of ischemic tolerance achieved by erythromycin preconditioning and will further the understanding of this clinically important new regimen of preemptive neuroprotection.